Use of sulfur containing initiators for anionic polymerization of monomers

ABSTRACT

A vulcanized rubber composition comprising the vulcanization product of a functional polymer, where the functional polymer is defined by the formula 
     
       
         
         
             
             
         
       
     
     where R is selected from C 1  to C 6  trialkyl-silyl groups, C 1  to C 20  alkyl groups, C 4  to C 20  cycloalkyl groups, C 6  to C 20  aryl groups, thienyl, furyl, and pyridyl groups; and R may optionally have attached thereto any of the following functional groups: C 1  to C 10  alkyl groups, C 6  to C 20  aryl groups, C 2  to C 10  alkenyl groups, C 3  to C 10  non-terminal alkynyl groups, ethers, tert-amines, oxazolines, thiazolines, phosphines, sulfides, silyls, and mixtures thereof; where R 1  is selected from C 2  to C 8  alkylene groups, where X is NR, and where π is a polymer chain.

This application is a continuation of U.S. application Ser. No.11/900,686, filed Sep. 13, 2007, which is a continuation of U.S.application Ser. No. 11/607,690, filed Dec. 2, 2006, which is acontinuation of U.S. application Ser. No. 10/533,408, filed on Apr. 29,2005, which are incorporated herein by reference, which is the NationalStage of International Application No. PCT/US03/34597, filed Oct. 30,2003, which claims the benefit of U.S. Provisional Ser. No. 60/455,508filed on Mar. 18, 2003, and U.S. Provisional Ser. No. 60/422,461 filedon Oct. 30, 2002.

FIELD OF THE INVENTION

This invention relates to functionalized polymers and rubbervulcanizates prepared therefrom.

BACKGROUND OF THE INVENTION

In the art of making tires, it is desirable to employ rubbervulcanizates that demonstrate reduced hysteresis loss, i.e., less lossof mechanical energy to heat. Hysteresis loss is often attributed topolymer free ends within the cross-linked rubber network, as well as thedisassociation of filler agglomerates.

Functionalized polymers have been employed to reduce hysteresis loss andincrease bound rubber. The functional group of the functionalizedpolymer is believed to reduce the number of polymer free ends. Also, theinteraction between the functional group and the filler particlesreduces filler agglomeration, which thereby reduces hysteretic lossesattributable to the disassociation of filler agglomerates (i.e. Payneeffect).

Selection of certain functionalized anionic-polymerization initiatorscan provide a polymer product having functionality at the head of thepolymer chain. A functional group can also be attached to the tail endof an anionically polymerized polymer by terminating a living polymerwith a functionalized compound.

Conjugated diene monomers are often anionically polymerized by usingorganometallic compounds as initiators. Exemplary organometallics thatare well-known as anionic-polymerization initiators for diene monomers,with and without monovinyl aromatic monomers, include alkyllithium,trialkyltin lithium, and certain aminolithium compounds. The synthesisof lithiodithiane reagents is known as is there addition to conjugatedketones. However, no use of sulfur containing initiators, particularlylithium thio acetal based compounds, is known for anionic polymerizationof dienes, trienes, monovinyl aromatics or combinations thereof.

Because functionalized polymers are advantageous, especially in thepreparation of tire compositions, there exists a need for additionalfunctionalized polymers. Moreover, because precipitated silica has beenincreasingly used as a reinforcing particulate filler in tires,functionalized elastomers having an affinity to both carbon black andsilica fillers are needed.

SUMMARY OF THE INVENTION

In general, the present invention advances the art by providing a neworganometallic anionic polymerization initiators for polymerizing diene,triene or monovinyl aromatic monomers, and combinations thereof.

The present invention also provides a method for anionicallypolymerizing monomers comprising the step of polymerizing the monomerswith a sulfur containing anionic initiator to provide a functional headgroup on the polymer.

The present invention also provides a polymer having a sulfur containingfunctional head group.

The present invention also provides a rubber composition having a sulfurcontaining functionalized polymer.

The present method further provides a pneumatic tire having at least onecomponent comprising a rubber compound containing a polymer having ahead group derived from a sulfur containing anionic initiator.

The functionalized polymers of this invention advantageously providecarbon black, carbon black/silica, and silica filled rubber vulcanizateshaving reduced hysteresis loss.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention provides sulfur containing lithio compounds,including lithio alkyl thio acetals and lithio aryl thio acetals, asinitiators for anionically polymerizing dienes, trienes, monovinylaromatics and combinations thereof. Suitable sulfur containing lithiocompounds have the general formula

where R is selected from C₁ to C₆ trialkyl-silyl groups, C₁ to C₂₀ alkylgroups, C₄ to C₂₀ cycloalkyl groups, C₆ to C₂₀ aryl groups, thienyl,furyl, and pyridyl groups; and R may optionally have attached theretoany of following functional groups: C₁ to C₁₀ alkyl groups, C₆ to C₂₀aryl groups, C₂ to C₁₀ alkenyl groups, C₃ to C₁₀ non-terminal alkynylgroups, ethers, tert-amines, oxazolines, thiazolines, phosphines,sulfides, silyls, and mixtures thereof; where R¹ is selected from thegroup consisting of C₂ to C₈ alkylene groups and where X is selectedfrom the group consisting of S, O and NR, wherein R is as defined above,and may optionally have attached thereto any of the above identifiedfunctional groups.

The sulfur containing lithio compounds having a tert-amine functionalgroup of the present invention have the general formula:

where R² is selected from the group consisting of C₁ to C₈ alkylenegroups, C₃ to C₁₂ cycloalkylene groups and C₆ to C₁₈ arylene groups; mis 0 to about 8; and R, R¹ and X are as defined above.

A preferred lithio alkyl thio acetal initiator is2-lithio-2-methyl-1,3-dithiane which can be represented as follows:

A preferred lithio aryl thio acetal initiator is2-lithio-2-phenyl-1,3-dithiane (PDT-Li). Its structure can berepresented as follows:

Other exemplary initiators of the present invention include:

The initiators of the present invention may be prepared by reacting aninitiator precursor compound with an organolithium compound, such as,n-butyllithium. These initiator precursors have the general formula:

where R, R¹ and X are as defined hereinabove.

As with the sulfur containing lithio compounds defined above, theinitiator precursors may also have attached to the R group any offollowing functional groups: C₁ to C₁₀ alkyl groups, C₆ to C₂₀ arylgroups, C₂ to C₁₀ alkenyl groups, C₃ to C₁₀ non-terminal alkynyl groups,ethers, tert-amines, oxazolines, thiazolines, phosphines, sulfides,silyls, and mixtures thereof. These functionalized precursor compoundscan then be reacted with an organolithium compound to form afunctionalized sulfur containing lithio initiator.

Several representative species of functionalized precursors are asfollows:

For a comprehensive summary of known functionalized phenyls, see thearticle “Recent advance in living anionic polymerization offunctionalized styrene derivatives”, by Hirao et al, Prog. Polym. Sci.(2002) 1399-1471, Elsevior, the subject matter of which is incorporatedherein by reference.

A non-limiting example of the synthesis of sulfur functionalizedinitiators, specifically 2-lithio-2-methyl-1,3-dithiane and2-lithio-2-phenyl-1,3-dithiane, from an initiator precursor andorganolithium compound prior to polymerization is as follows:commercially available solutions of 2-methyl-1,3-dithiane or2-phenyl-1,3-dithiane are added to dried tetrahydrofuran, and cooled toapproximately −78° C. A solution comprising butyllithium and hexane isthen added thereto. The resulting solution is then stirred forapproximately 3 hours and allowed to stand overnight at a temperature ofless than about 10° C. The resulting solutions may then be used toinitiate anionic polymerization. This type of initiator preparation mayoccur in any appropriate reaction vessel, including a polymerizationreactor, prior to the addition of a monomer(s) solution.

Depending on the stability of the initiator precursor, it may bedesirable to prepare the initiator in situ, as opposed to preparing andstoring said precursor. The dithiane initiators of the present inventioncan be synthesized in situ in a solution comprising the monomer ormonomers to be polymerized. Generally, the in situ preparation ofanionic initiator is practiced by creating a solution comprising apolymerization solvent, and the monomer(s) to be polymerized. This firstsolution is generally heated to about −80° C. to about 100° C., and morepreferably from about −40° C. to about 50° C., and most preferable fromabout 0° C. to about 25° C., and the non-lithiated initiator precursorand organolithium are added thereto. The solution is then heated to atemperature within the range of about −80° C. to about 150° C., and morepreferably from about 25° C. to about 120° C. and most preferably fromabout 50° C. to about 100° C. and allowed to react for a period of timeof from about 0.02 hours to about 168 hours, more preferably from about0.08 hours to about 48 hours, and most preferably from about 0.16 hoursto about 2 hours, or as sufficient to result in the formation of asolution (cement) containing the desired functional polymer. Reactiontimes and temperatures may vary as necessary to allow the precursor andorganolithium to react, and subsequently polymerize the monomersolution.

A non-limiting example of an in-situ initiator synthesis involvescreating a solution comprising hexane, styrene monomer, and butadiene.This first solution is heated to about 24° C. and 2-methyl-1,3-dithianeand butyllithium are added thereto. The solution is then heated toapproximately 54° C. and allowed to react for approximately 40 minutes.

The initiators of the present invention are useful for functionalizingan anionically polymerized living polymer. These functionalized polymersare formed by reacting a functionalized anionic initiator with certainunsaturated monomers to propagate a polymeric structure. Thefunctionalized polymer may be defined by the formula

where R is selected from C₁ to C₆ trialkyl-silyl groups, C₁ to C₂₀ alkylgroups, C₄ to C₂₀ cycloalkyl groups, C₆ to C₂₀ aryl groups, thienyl,furyl, and pyridyl groups; and R may optionally have attached theretoany of the following functional groups: C₁ to C₁₀ alkyl groups, C₆ toC₂₀ aryl groups, C₂ to C₁₀ alkenyl groups, C₃ to C₁₀ non-terminalalkynyl groups, ethers, tert-amines, oxazolines, thiazolines,phosphines, sulfides, silyls, and mixtures thereof; where R¹ is selectedfrom C₂ to C₈ alkylene groups, where X is selected from S, O and NR,where R is defined above, and may optionally have attached thereto anyof the above identified functional groups and where T is a polymerchain.

Throughout the formation propagation of the polymer, the polymericstructure is anionic and “living.” A new batch of monomer subsequentlyadded to the reaction can add to the living ends of the existing chainsand increase the degree of polymerization. A living polymer, therefore,is a polymeric segment having a living or reactive end. Anionicpolymerization is further described in George Odian, Principles ofPolymerization, ch. 5 (3^(rd) Ed. 1991), or Panek, 94 J. Am. Chem. Soc.,8768 (1972), which are incorporated herein by reference.

The sulfur containing lithio alkyl thio acetals and sulfur containinglithio aryl thio acetals can be used as anionic polymerizationinitiators in amounts varying widely based upon the desired polymercharacteristics. In one embodiment it is preferred to employ from about0.1 to about 100, and more preferably from about 0.33 to about 10 mmolof lithium per 100 g of monomer.

Monomers that can be employed in preparing an anionically polymerizedliving polymer include any monomer capable of being polymerizedaccording to anionic polymerization techniques. These monomers includethose that lead to the formation of elastomeric homopolymers orcopolymers. Suitable monomers include, without limitation, conjugatedC₄-C₁₂ dienes, C₄-C₁₈ monovinyl aromatic monomers and C₆-C₂₀ trienes.Examples of conjugated diene monomers include, without limitation,1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, and1,3-hexadiene. A non-limiting example of trienes includes myrcene.Aromatic vinyl monomers include, without limitation, styrene,alpha-methyl styrene, p-methylstyrene, and vinylnaphthalene. Whenpreparing elastomeric copolymers, such as those containing conjugateddiene monomers and aromatic vinyl monomers, the conjugated dienemonomers and aromatic vinyl monomers are normally used at a ratio of95:5 to 50:50, and preferable 95:5 to 65:35.

Anionic polymerizations are typically conducted in a polar solvent, suchas tetrahydrofuran (THF), or a non-polar hydrocarbon, such as thevarious cyclic and acyclic hexanes, heptanes, octanes, pentanes, theiralkylated derivatives, and mixtures thereof, as well as benzene.

In order to promote randomization in copolymerization and to controlvinyl content, a polar coordinator may be added to the polymerizationingredients. Amounts range between 0 and 90 or more equivalents perequivalent of lithium. The amount depends on the amount of vinyldesired, the level of styrene employed and the temperature of thepolymerization, as well as the nature of the specific polar coordinator(modifier) employed. Suitable polymerization modifiers include forexample, ethers, or amines to provide the desired microstructure andrandomization of the comonomer units.

Compounds useful as polar coordinators include those having an oxygen ornitrogen heteroatom and a non-bonded pair of electrons. Examples includedialkyl ethers of mono and oligo alkylene glycols; “crown” ethers;tertiary amines such as tetramethylethylene diamine (TMEDA); linear THFoligomers; and the like. Specific examples of compounds useful as polarcoordinators include tetrahydrofuran (THF), linear and cyclic oligomericoxolanyl alkanes such as 2,2-bis(2′-tetrahydrofuryl) propane,dipiperidyl ethane, dipiperidyl methane, hexamethylphosphoramide,N—N′-dimethylpiperazine, diazabicyclooctane, dimethyl ether, diethylether, tributylamine and the like. The linear and cyclic oligomericoxolanyl alkane modifiers are described in U.S. Pat. No. 4,429,091,incorporated herein by reference.

To terminate the polymerization, and thus further control polymermolecular weight, a terminating agent, coupling agent or linking agentmay be employed, all of these agents being collectively referred toherein as “terminating reagents”. Useful terminating, coupling orlinking agents include active hydrogen compounds such as water oralcohol. Certain of these reagents may provide the resulting polymerwith multi-functionality. That is, the polymers initiated according tothe present invention, may carry the functional head group as discussedhereinabove, and may also carry a second functional group as a result ofthe terminating reagents, coupling agents and linking agents used in thepolymer synthesis.

Useful functional terminating reagents are those disclosed in U.S. Pat.Nos. 5,502,131, 5,496,940 and 4,616,069, the subject matters of whichare incorporated herein by reference, and include tin tetrachloride,(R)₃SnCl, (R)₂SnCl₂, RSnCl₃, carbodiimides, N-cyclic amides, N,N′disubstituted cyclic ureas, cyclic amides, cyclic ureas, isocyanates,Schiff bases, 4,4′-bis(diethylamino) benzophenone, alkylthiothiazolines, carbon dioxide and the like. Other agents include thealkoxy silanes Si(OR)₄, RSi(OR)₃, R₂Si(OR)₂ cyclic siloxanes andmixtures thereof. The organic moiety R is selected from the groupconsisting of alkyls having from 1 to about 20 carbon atoms, cycloalkylshaving from about 3 to about 20 carbon atoms, aryls having from about 6to about 20 carbon atoms and aralkyls having from about 7 to about 20carbon atoms. Typical alkyls include n-butyl, s-butyl, methyl, ethyl,isopropyl and the like. The cycloalkyls include cyclohexyl, menthyl andthe like. The aryl and the aralkyl groups include phenyl, benzyl and thelike. Preferred endcapping agents are tin tetrachloride, tributyl tinchloride, dibutyl tin dichloride, tetraethylorthosilicate and1,3-dimethyl-2-imidazolidinone (DMI). The foregoing listing ofterminating reagents is not to be construed as limiting but rather asenabling. While a terminating reagent can be employed, practice of thepresent invention is not limited to a specific reagent or class of suchcompounds.

While terminating to provide a functional group on the terminal end ofthe polymer is preferred, it is further preferred to terminate by acoupling reaction, with for example, tin tetrachloride or other couplingagent such as silicon tetrachloride (SiCl₄), esters and the like.

Anionically polymerized living polymers can be prepared by either batch,semi-batch or continuous methods. A batch polymerization is begun bycharging a blend of monomer(s) and normal alkane solvent to a suitablereaction vessel, followed by the addition of the polar coordinator (ifemployed) and an initiator compound. The reactants are heated to atemperature of from about 20 to about 130° C. and the polymerization isallowed to proceed for from about 0.1 to about 24 hours. This reactionproduces a reactive polymer having a reactive or living end. Preferably,at least about 30% of the polymer molecules contain a living end. Morepreferably, at least about 50% of the polymer molecules contain a livingend. Even more preferably, at least about 80% contain a living end.

A continuous polymerization is begun by charging monomer(s), initiatorand solvent at the same time to a suitable reaction vessel. Thereafter,a continuous procedure is followed that removes the product after asuitable residence time and replenishes reactants.

In a semi-batch polymerization the reaction medium and initiator areadded to a reaction vessel, and the monomer(s) is continuously addedover time at a rate dependent on temperature, monomer/initiator/modifierconcentrations, etc. Unlike a continuous polymerization, the product isnot continuously removed from the reactor.

Molecular weight of the polymers prepared using the initiators of thepresent invention can be determined by number average molecular weight(M_(n)) and weight average molecular weight (M_(w)). For polybutadienepolymers, M_(n) values range from about 0.5 kg/mol to about 500 kg/mol.For copolymers, such as SBR, M_(n) values range from about 0.5 kg/mol toabout 500 kg/mol.

After formation of the functional polymer, a processing aid and otheroptional additives such as oil can be added to the polymer cement. Thefunctional polymer and other optional ingredients are then isolated fromthe solvent and preferably dried. Conventional procedures fordesolventization and drying may be employed. In one embodiment, thefunctional polymer may be isolated from the solvent by steamdesolventization or hot water coagulation of the solvent followed byfiltration. Residual solvent may be removed by using conventional dryingtechniques such as oven drying or drum drying. Alternatively, the cementmay be directly drum dried.

The functionalized polymers, and rubber compositions containing suchfunctionalized polymers, of this invention are particularly useful inpreparing tire components. These tire components can be prepared byusing the functionalized polymers of this invention alone or togetherwith other rubbery polymers. Other rubbery elastomers that may be usedinclude natural and synthetic elastomers. The synthetic elastomerstypically derive from the polymerization of conjugated diene monomers.These conjugated diene monomers may be copolymerized with other monomerssuch as vinyl aromatic monomers. Other rubbery elastomers may derivefrom the polymerization of ethylene together with one or morealpha-olefins and optionally one or more diene monomers.

Useful rubbery elastomers include natural rubber, syntheticpolyisoprene, polybutadiene, polyisobutylene-co-isoprene, neoprene,poly(ethylene-co-propylene), poly(styrene-co-butadiene),poly(styrene-co-isoprene), poly(styrene-co-isoprene-co-butadiene),poly(isoprene-co-butadiene), poly(ethylene-co-propylene-co-diene),polysulfide rubber, acrylic rubber, urethane rubber, silicone rubber,epichlorohydrin rubber, and mixtures thereof. These elastomers can havea myriad of macromolecular structures including linear, branched andstar shaped. Preferred elastomers include natural rubber, isoprene,styrene-butadiene copolymers, and butadiene rubber because of theircommon usage in the tire industry.

The rubber compositions may include fillers such as inorganic andorganic fillers. The organic fillers include carbon black and starch.The inorganic fillers may include silica, aluminum hydroxide, magnesiumhydroxide, clays (hydrated aluminum silicates), and mixtures thereof.Preferred fillers are carbon black, silica and mixtures thereof.

The elastomers can be compounded with all forms of carbon black alone,or in a mixture with silica. The carbon black can be present in amountsranging from about 0 to about 100 phr, with about five to about 80 phrbeing preferred. When both carbon black and silica are employed incombination as the reinforcing filler, they are often used in a carbonblack-silica ratio of about 10:1 to about 1:4.

The carbon blacks can include any of the commonly available,commercially-produced carbon blacks, but those having a surface area(EMSA) of at least 20 m²/g and, more preferably, at least 35 m²/g up to200 m²/g or higher are preferred. Surface area values used in thisapplication are determined by ASTM D-1765 using thecetyltrimethyl-ammonium bromide (CTAB) technique. Among the usefulcarbon blacks are furnace black, channel blacks and lamp blacks. Morespecifically, examples of useful carbon blacks include super abrasionfurnace (SAF) blacks, high abrasion furnace (HAF) blacks, fast extrusionfurnace (FEF) blacks, fine furnace (FF) blacks, intermediate superabrasion furnace (ISAF) blacks, semi-reinforcing furnace (SRF) blacks,medium processing channel blacks, hard processing channel blacks andconducting channel blacks. Other carbon blacks which can be utilizedinclude acetylene blacks. A mixture of two or more of the above blackscan be used in preparing the carbon black products of the invention. Thecarbon blacks utilized in the preparation of the vulcanizableelastomeric compositions of the invention can be in pelletized form oran unpelletized flocculent mass. Preferably, for more uniform mixing,unpelletized carbon black is preferred.

Examples of suitable silica reinforcing filler include, but are notlimited to, precipitated amorphous silica, wet silica (hydrated silicicacid), dry silica (anhydrous silicic acid), fumed silica, calciumsilicate, and the like. Other suitable fillers include aluminumsilicate, magnesium silicate, and the like. Among these, precipitatedamorphous wet-process, hydrated silicas are preferred. These silicas areso-called precipitated because they are produced by a chemical reactionin water, from which they are precipitated as ultra-fine, sphericalparticles. These primary particles strongly associate into aggregates,which in turn combine less strongly into agglomerates. The surface area,as measured by the BET method gives the best measure of the reinforcingcharacter of different silicas. For silicas of interest for the presentinvention, the surface area should be about 32 m²/g to about 400 m²/g,with the range of about 100 m²/g to about 250 m²/g being preferred, andthe range of about 150 m²/g to about 220 m²/g being most preferred. ThepH of the silica filler is generally about 5.5 to about 7 or slightlyover, preferably about 5.5 to about 6.8.

Silica can be employed in the amount of about 0 to about 100 phr,preferably in an amount of about 5 to about 80 phr and, more preferably,in an amount of about 30 to about 80 phr. The useful upper range islimited by the high viscosity imparted by fillers of this type. Some ofthe commercially available silicas which can be used include, but arenot limited to, Hi-Sil® 190, Hi-Sil® 210, Hi-Sil® 215, Hi-Sil® 233,Hi-Sil® 243, and the like, produced by PPG Industries (Pittsburgh, Pa.).A number of useful commercial grades of different silicas are alsoavailable from Degussa Corporation (e.g., VN2, VN3), Rhone Poulenc(e.g., Zeosil® 1165 MP), and J.M. Huber Corporation.

The elastomeric compounds of the invention can optionally furtherinclude a silica coupling agent such as, but not limited to, amercaptosilane, a bis(trialkoxysilylorgano) polysulfide, a3-thiocyanatopropyl trimethoxysilane, or the like, or any of the silicacoupling agents that are known to those of ordinary skill in the rubbercompounding art. Exemplary mercaptosilanes include, but are not limitedto, 1-mercaptomethyltriethoxysilane, 2-mercaptoethyltriethoxysilane,3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyl-diethoxysilane,2-mercaptoethyltriproxysilane, 18-mercaptooctadecyldiethoxychlorosilane,and the like. Exemplary bis(trialkoxysilylorgano) polysulfide silicacoupling agents include, but are not limited to,bis(3-triethoxysilyl-propyl) tetrasulfide (TESPT), which is soldcommercially under the tradename Si69 by Degussa Inc., New York, N.Y.,and bis(3-triethoxysilylpropyl) disulfide (TESPD) or Si75, availablefrom Degussa, or Silquest® A1589, available from Crompton. Thepolysulfide organosilane silica coupling agent can be present in anamount of about 0.01% to about 20% by weight, based on the weight of thesilica, preferably about 0.1% to about 15% by weight, and especiallyabout 1% to about 10%.

Compounding involving silica fillers is also disclosed in U.S. Pat. Nos.6,221,943, 6,342,552, 6,348,531, 5,916,961, 6,252,007, 6,369,138,5,872,176, 6,180,710, 5,866,650, 6,228,908 and 6,313,210, thedisclosures of which are incorporated by reference herein.

The elastomeric compositions are compounded or blended by using mixingequipment and procedures conventionally employed in the art, such asmixing the various vulcanizable polymer(s) with reinforcing fillers andcommonly used additive materials such as, but not limited to, curingagents (for a general disclosure of suitable vulcanizing agents one canrefer to Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd ed.,Wiley Interscience, N.Y. 1982, Vol. 20, pp. 365-468, particularly“Vulcanization Agents and Auxiliary Materials” pp. 390-402), activators,retarders and accelerators; processing additives, such as oils; resins,including tackifying resins; plasticizers; pigments; additional fillers;fatty acid; zinc oxide; waxes; antioxidants; antiozonants; peptizingagents; and the like. As known to those skilled in the art, theadditives mentioned above are selected and commonly used in conventionalamounts. For example, without limitation, a tire component compoundtypically contains elastomers, fillers, processing oils/aids,antidegradants, zinc oxide, stearic acid, sulfur, accelerators andcoupling agents. Such compounds can have such additional ingredients inthe following amounts:

fillers: from about 0 to about 150 phr, and preferably from about 30 toabout 80 phr;

processing oils/aids: from about 0 to about 75 phr, and preferably fromabout 0 to about 40 phr;

antidegradants: from about 0 to about 10 phr, and preferably from about0 to about 5 phr;

stearic acid: from about 0 to about 5 phr, and preferably from about 0to about 3 phr;

zinc oxide: from about 0 to about 10 phr, and preferably from about 0 toabout 5 phr;

sulfur: from about 0 to about 10 phr, and preferably from about 0 toabout 4 phr;

accelerators: from about 0 to about 10 phr, and preferably from about 0to about 5 phr; and

coupling agent: from about 0 to about 30 phr, and preferably from about5 to about 15 phr.

Preferably, an initial master batch is prepared that includes the rubbercomponent and the reinforcing fillers, as well as other optionalnon-curative additives, such as processing oil, antioxidants, and thelike. After the master batch is prepared, one or more optional remillstages can follow in which either no ingredients are added to the firstmixture, or the remainder of the non-curing ingredients are added, inorder to reduce the compound viscosity and improve the dispersion of thereinforcing filler. The final step of the mixing process is the additionof vulcanizing agents to the mixture.

The resulting elastomeric compounds when vulcanized using conventionalrubber vulcanization conditions exhibit reduced hysteresis propertiesand are particularly adapted for use as tread rubbers for tires havingreduced rolling resistance. Accordingly, the present invention providesa vulcanized rubber composition comprising at least one vulcanizedrubber deriving from a vulcanizable rubber defined by the formula

where R is selected from C₁ to C₆ trialkyl-silyl groups, C₁ to C₂₀ alkylgroups, C₄ to C₂₀ cycloalkyl groups, C₆ to C₂₀ aryl groups, thienyl,furyl, and pyridyl groups; and R may optionally have attached theretoany of the following functional groups: C₁ to C₁₀ alkyl groups, C₆ toC₂₀ aryl groups, C₂ to C₁₀ alkenyl groups, C₃ to C₁₀ non-terminalalkynyl groups, ethers, tert-amines, oxazolines, thiazolines,phosphines, sulfides, silyls, and mixtures thereof; where R¹ is selectedfrom C₂ to C₈ alkylene groups, where X is selected from S, O and NR,where R is defined above, and may optionally have attached thereto anyof the above identified functional groups and where π is a polymerchain.

Further embodiments of the invention are described in the followingexamples.

General Experimental Testing Procedures

Molecular Weight Determination: Molecular weights were measured by gelpermeation chromatography (GPC) using a Waters Model 150-C instrumentequipped with a Model 2414 Refractometer and a Model 996 PhotodiodeArray Detector (UV). Molecular weights were calculated from a universalcalibration curve based on polystyrene standards and corrected using thefollowing Mark-Houwink constants for SBR: k=0.000269, α=0.73.

Styrene and Vinyl Content and Small Molecule Structure Confirmation:Styrene and vinyl content, and small molecule structure confirmationwere determined using ¹H-NMR (CDCl₃) and ¹³C NMR measurements on a 300MHz Gemini 300 NMR Spectrometer System (Varian).

Glass Transition Temperature (T_(g)): The glass transition temperaturewas determined using a DSC 2910 Differential Scanning Calorimeter (TAInstruments). The T_(g) was determined as the temperature where aninflection point occurred in the heat capacity (C_(p)) change.

Dynamic Mechanical Properties: The dynamic mechanical properties weremeasured using two techniques. A Rheometrics Dynamic Analyzer RDAII(Rheometric Scientific) in the parallel plate mode was used with 15 mmthick, 9.27 mm diameter buttons. The loss modulus, G″, storage modulus,G′, and tan δ were measured over deformation of 0.25-14.5% at 1 Hz and50° C. The Payne Effect was estimated by calculating the difference ofG′ (0.25% E)-G′ (14.0% E). A RDA700 (Rheometric Scientific) in thetorsion rectangular mode was also used with samples having thedimensions 31.7 mm×12.7 mm×2.0 mm. The temperature was increased at arate of 5° C. min⁻¹ from −80° C. to 100° C. The moduli (G′ and G″) wereobtained using a frequency of 5 Hz and a deformation of 0.5% from −80°C. to −10° C. and 2% from −10° C. to 100° C.

Mooney Viscosity: Mooney viscosity measurements were conducted accordingto ASTM-D 1646-89.

Tensile: The tensile mechanical properties were measured according toASTM-D 412 (1998) Method B at 25° C. The tensile test specimens arerings with a dimension of 1.27 mm width and 1.90 mm thick. A specificgauge length of 25.4 mm is used for the tensile test.

Cure: In the present invention, cure is measured utilizing moving dierheometer (MDR) according to ASTM D2084 (1995).

Bound Rubber: Bound rubber, a measure of the percentage of rubber bound,through some interaction to the filler, was determined by solventextraction with toluene at room temperature. More specifically, a testspecimen of each uncured rubber formulation was placed in toluene for 3days. The solvent was removed and the residue was dried and weighed. Thepercentage of bound rubber was then determined according to the formula

% bound rubber=[100(w _(d) −F)]/R

where w_(d) is the weight of the dried residue, F is the weight of thefiller and any other solvent insoluble matter in the original sample andR is the weight of rubber in the original sample.

Thin Layer Chromatography (TLC): TLC was done on Sigma-Aldrich TLCplates, silica gel on aluminum.

Column Chromatography Column chromatography was conducted using silicagel sorbent (200-425 Mesh, Fisher Scientific).

General Experimental

In order to demonstrate practice of the present invention, the followingexamples have been prepared and tested.

A dried 28 oz (0.8 L) or 7 oz (0.2 L) glass bottle, which previously hadbeen sealed with extracted septum liners and perforated crown caps undera positive nitrogen purge, was used for all of the preparations.

Dried butadiene in hexane (21 to 23 weight percent butadiene), driedstyrene in hexane (styrene blend, 33 weight percent styrene), driedhexane, n-butyllithium (1.68 M in hexane), cyclic oligomeric oxolanylalkane modifier in hexane (1.6 M solution in hexane, stored over calciumhydride), and butylated hydroxytoluene (BHT) solution in hexane wereused. Tetrahydrofuran (THF) was distilled from potassium benzophenoneketyl.

Commercially available reagents and starting materials (Aldrich Chem.Co. and Fisher Scientific) include the following: 2-methyl-1,3-dithiane;2-trimethylsilyl-1,3-dithiane; 2-methylthio-2-thiazoline; tetraethylorthosilicate; 1-bromo-3-chloropropane; 2-phenyl-1,3-dithiane,benzaldehyde dimethyl acetal, 4-(dimethylamino) benzaldehyde;4-(dibutylamino) benzaldehyde; 1,3-propanedithiol;3-mercapto-1-propanol; 1,3-dimethyl-2-imidazolidinone (DMI); tributyltinchloride and tin(IV) chloride, which were used as purchased withoutfurther purification.

The examples should not, however, be viewed as limiting the scope of theinvention. The claims will serve to define the invention.

EXAMPLES Example No. 1 Synthesis of 2-lithio-2-methyl-1,3-dithiane

To a 0.8 L N₂ purged bottle equipped with a serum cap was added 350 mLof dried tetrahydrofuran and 10 mL of 2-methyl-1,3-dithiane (83.5 mmol).The bottle was cooled to −78° C. and 55.83 mL of 1.510 M butyllithium(84.3 mmol) in hexane was added. The reaction was stirred at −78° C. for3 hours and then stored at −25° C. overnight. Titration of the resultingsolution indicated that the solution contained 0.234 M active lithiumcompound. To elucidate the structure of this compound, the solution wasadded to a dried solution of 8.26 mL of 1-bromo-3-chloropropane (83.5mmol) in 90 mL tetrahydrofuran at −78° C. After 3 hours, the productswere examined by GC/MS and found to contain >95%2-(3-chloropropyl)-2-methyl-1,3-dithiane. No 1-chloroheptane wasobserved indicating that the butyllithium had completely reacted withthe 2-methyl-1,3-dithiane.

Example No. 2 Synthesis of Poly(styrene-co-butadiene) with2-lithio-2-methyl-1,3-dithiane

To a 1.75 L N₂ purged reactor equipped with a stirrer was added 1.12 kgof hexane, 0.48 kg of 33 wt % styrene in hexane, and 2.89 kg of 22.0 wt% butadiene in hexane. The reactor was then heated to 24° C. and 0.5 mLof 1.6 M of a cyclic oligomeric oxolanyl alkane modifier, in hexane and22.63 mL of 0.234 M 2-lithio-2-methyl-1,3-dithiane in tetrahydrofuranwas charged to the reactor. The reactor jacket was then heated to 54° C.After 15 minutes, the batch temperature peaked at 76.5° C. After anadditional 25 minutes, the cement was removed from the reactor,coagulated in isopropanol containing butylated hydroxy toluene (BHT),and drum dried to yield a polymer with the following properties:M_(n)=153 kg/mol, M_(w)=167 kg/mol, T_(g)=−44.4° C., 21.7% styrene, 1.3%block styrene, 32.1% vinyl, and 46.2% 1,4 butadiene incorporation.

Example No. 3 Synthesis of Poly(styrene-co-butadiene) with2-lithio-2-methyl-1,3-dithiane

To a 1.75 L N₂ purged reactor equipped with a stirrer was added 1.12 kgof hexane, 0.48 kg of 33 wt % styrene in hexane, and 2.89 kg of 22.0 wt% butadiene in hexane. The reactor was then heated to 24° C. and 0.5 mLof 1.6 M of cyclic oligomeric oxolanyl alkane modifier in hexane and16.96 mL of 0.234 M 2-lithio-2-methyl-1,3-dithiane in tetrahydrofuranwas charged to the reactor. The reactor jacket was then heated to 54° C.After 17 minutes, the batch temperature peaked at 75.7° C. After anadditional 10 minutes, the cement was removed from the reactor,coagulated in isopropanol containing butylated hydroxy toluene (BHT),and drum dried to yield a polymer with the following properties:M_(n)=208 kg/mol, M_(w)=240 kg/mol, T_(g)=−43.8° C., 22.2% styrene, 1.6%block styrene, 31.2% vinyl, and 46.5% 1,4 butadiene incorporation.

Example No. 4 Synthesis of Poly(styrene-co-butadiene) with In Situ2-lithio-2-methyl-1,3-dithiane

To a 1.75 L N₂ purged reactor equipped with a stirrer was added 1.07 kgof hexane, 0.48 kg of 33 wt % styrene in hexane, and 2.95 kg of 21.6 wt% butadiene in hexane. The reactor was then heated to 24° C. and 0.5 mLof 1.6 M of cyclic oligomeric oxolanyl alkane modifier in hexane and8.47 mL of 0.5 M 2-methyl-1,3-dithiane in hexane, and 3.42 mL of 1.55 Mbutyllithium in hexanes was charged to the reactor. The reactor jacketwas then heated to 54° C. After 28 minutes, the batch temperature peakedat 68.6° C. After an additional 10 minutes, the cement was removed fromthe reactor, coagulated in isopropanol containing butylated hydroxytoluene (BHT), and drum dried to yield a polymer with the followingproperties: M_(n)=135 kg/mol, M_(w)=142 kg/mol, T_(g)=−56.6° C.

Comparative Example No. 5 Synthesis of Poly(styrene-co-butadiene) withbutyllithium

To a 1.75 L N₂ purged reactor equipped with a stirrer was added 1.07 kgof hexane, 0.48 kg of 33 wt % styrene in hexane, and 2.95 kg of 21.6 wt% butadiene in hexane. The reactor was then heated to 24° C. and 0.5 mLof 1.6 M of cyclic oligomeric oxolanyl alkane modifier in hexane and22.6 mL tetrahydrofuran and 3.42 mL 1.55 M butyllithium in hexane wascharged to the reactor. The reactor jacket was then heated to 54° C.After 15 minutes, the batch temperature peaked at 71.2° C. After anadditional 10 minutes, the cement was removed from the reactor,coagulated in isopropanol containing butylated hydroxy toluene (BHT),and drum dried to yield a polymer with the following properties:M_(n)=157 kg/mol, M_(w)=168 kg/mol, T_(g)=−42.5° C., 21.3% styrene, 1.1%block styrene, 33.8% vinyl, and 45.0% 1,4 butadiene incorporation.

Comparative Example No. 6 Synthesis of Poly(styrene-co-butadiene) withbutyllithium

To a 1.75 L N₂ purged equipped with a stirrer was added 1.07 kg ofhexane, 0.48 kg of 33 wt % styrene in hexane, and 2.95 kg of 21.6 wt %butadiene in hexane. The reactor was then heated to 24° C. and 0.5 mL of1.6 M of cyclic oligomeric oxolanyl alkane modifier in hexane and 16.96mL tetrahydrofuran and 2.56 mL 1.55 M butyllithium in hexane was chargedto the reactor. The reactor jacket was then heated to 54° C. After 17minutes, the batch temperature peaked at 75.5° C. After an additional 10minutes, the cement was removed from the reactor, coagulated inisopropanol containing butylated hydroxy toluene (BHT), and drum driedto yield a polymer with the following properties: M_(n)=190 kg/mol,M_(w)=207 kg/mol, T_(g)=−44.0° C., 22.1% styrene, 1.3% block styrene,32.1% vinyl, and 45.9% 1,4 butadiene incorporation.

Next, three polybutadiene examples were prepared, Nos. 7-9, usingbutyllithium (control), 2-litho-2-methyl-1,3-dithiane and2-lithio-2-trimethylsilyl-1,3-dithiane initiators, both dithiane beingprepared in situ.

Comparative Example No. 7 Synthesis of Control Polybutadiene Initiatedby Butyllithium

To a 0.8 L nitrogen purged bottle equipped with a serum cap was added0.47 mL of 1.6M butyl lithium in hexane. Then, 27.3 g of hexane and272.7 g of 22.0% butadiene in hexane were added. The reaction was heatedto 50° C. for 4 hours. The resulting polymer solution was coagulated inisopropanol containing butylated hydroxy toluene (BHT), and drum driedto yield a polymer with the following properties: M_(n)=88.2 kg/mol,M_(w)=104.5 kg/mol, M_(w)/M_(n)=1.18, T_(g)=−94.2° C.

Example No. 8 Synthesis of Polybutadiene Initiated by In Situ Generated2-litho-2-methyl-1,3-dithiane

To a 0.8 L nitrogen purged bottle equipped with a serum cap was added0.59 mL of 0.5M 2-methyl-1,3-dithiane and 0.47 mL of 1.6M butyl lithiumin hexane. Then, 27.3 g of hexane and 272.7 g of 22.0% butadiene inhexane were added. The reaction was heated to 50° C. for 4 hours. Theresulting polymer solution was coagulated in isopropanol containing BHT,and drum dried to yield a polymer with the following properties:M_(n)=101.6 kg/mol, M_(w)=127.5 kg/mol, M_(w)/M_(n)=1.26, T_(g)=−94.6°C.

Example No. 9 Synthesis of Polybutadiene Initiated by In Situ Generated2-lithio-2-trimethylsilyl-1,3-dithiane

To a 0.8 L nitrogen purged bottle equipped with a serum cap was added0.29 mL of 1.0M 2-trimethylsilyl-1,3-dithiane and 0.47 mL of 1.6M butyllithium in hexane. Then, 27.3 g of hexane and 272.7 g of 22.0% butadienein hexane were added. The reaction was heated to 50° C. for 4 hours. Theresulting polymer solution was coagulated in isopropanol containing BHTand drum dried to yield a polymer with the following properties:M_(n)=81.9 kg/mol, M_(w)=125.9 kg/mol, M_(w)/M_(n)=1.54, T_(g)=−93.9° C.

The three polybutadiene polymers were subsequently compounded with otheringredients to prepare vulcanizable elastomeric compounds. Componentparts by weight, per 100 parts of rubber (phr) are set forth in Table I.

TABLE I Vulcanizable Elastomeric Compounds MASTERBATCH Compound CompoundCompound Example 10 Example 11 Example 12 Polymer Example 7 100 0 0Polymer Example 8 0 100 0 Polymer Example 9 0 0 100 Carbon Black 50 5050 Wax and Aromatic Oil 11.5 11.5 11.5 Stearic Acid 2 2 2 Antioxidant 11 1 Total 164.5 164.5 164.5 FINAL MIX Example 10 Example 11 Example 12Initial 164.5 164.5 164.5 Accelerators 1.2 1.2 1.2 Zinc Oxide 2 2 2Sulfur 1.3 1.3 1.3 Total 169.0 169.0 169.0

The masterbatches were prepared by mixing the initial compounds in a 300g Brabender mixer operating at 60 rpm and 133° C. First, the polymer (ofExamples 7, 8 and 9, respectively) was placed in the mixer, and after0.5 minutes, the remaining ingredients except the stearic acid wereadded. The stearic acid was then added after 3 minutes. The initialcomponents were mixed for 5-6 minutes. At the end of mixing thetemperature was approximately 165° C. Each sample was transferred to amill operating at a temperature of 60° C., where it was sheeted andsubsequently cooled to room temperature.

The final components were mixed by adding the masterbatch and thecurative materials to the mixer simultaneously. The initial mixertemperature was 65° C. and it was operating at 60 rpm. The finalmaterial was removed from the mixer after 2.25 minutes when the materialtemperature was between 100 to 105° C. The finals were sheeted intoDynastat buttons and 6×6×0.075 inch (15×15×0.1875 cm) sheets. Thesamples were cured at 171° C. for 15 minutes in standard molds placed ina hot press.

The resulting elastomeric compounds of Example Nos. 10-12 were thensubjected to physical testing, the results of which are reported inTable II.

TABLE II Physical Properties of Compounded Stocks Compound ExampleCompound Compound 10 Example Example Property (Control) 11 12 MH (kg-cm)0.73 1.02 1.09 ML (kg-cm) 15.92 17.54 15.8 TS₂ (min) 1.38 1.24 1.27 200%Modulus @23° C. 2.73 2.81 2.66 (MPa) T_(b) @23° C. (MPa) 11.89 14.4213.95 E_(b) @23° C. (%) 593.7 617.7 628.5 tan δ 7% E, 65° 0.234 0.1880.195 ΔG′ (50° C.) (MPa)* 2.120 1.746 1.680 *ΔG′ = G′ (@0.25% E) − G′(@14.5% E)

The data in Table II establishes a reduced tan δ (improved hysteresis)for the elastomeric compounds containing polymers carrying functionalheadgroups from the initiator (Compound Examples 11 and 12) compared tothe control compound (Example 10) containing the polymer of Example No.7. Note that both tan δ and ΔG′ are lower that the control, Example 10,indicating that dithiane functionalized polymers interact with thefillers. The lower tan δ and ΔG′ values also indicate that tires madewith such rubber should have lower rolling resistance properties. Thenext set of examples demonstrates the use of lithio aryl thio acetals asinitiators.

Example No. 13 Synthesis of 2-lithio-2-phenyl-1,3-dithiane

To a solution of 2-phenyl-1,3-dithiane (2.1 g, 10.69 mmol) in THF (5 mL)and cyclohexane (10 mL) was added n-BuLi (6.37 mL, 1.68 M in hexane)dropwise via a syringe at −78° C. The solution was stirred for anadditional 3 hours at 0° C. The resulting 0.5 M2-litho-2-phenyl-1,3-dithiane (abbreviated as PDT-Li) was used foranionic initiator for polymerizing butadiene and/or butadiene/styreneand stored in an inert atmosphere of nitrogen in a refrigerator.

Example No. 14 Synthesis of 2-phenyl-1,3-oxathiane

To an oven-dried 250 mL flask fitted with a magnetic stirring bar andreflux condenser was introduced 0.4 g of Montmorillonite KSF, 1.65 g(10.8 mmol) of benzaldehyde dimethyl acetal in 35 mL of THF, followed by1.0 g (10.8 mmol) of 3-mecapto-1-propanol in 5 mL of THF. The mixturewas refluxed under nitrogen for 12 hours. After cooling to roomtemperature and filtered, the filtrate was washed with saturated NaHCO₃(2×20 mL), saturated NaCl (20 mL) and dried over MgSO₄ (anhydrous). Thesolvent was evaporated; a chromatograph using silica gel [elution withHexane/Et₂O (70/30)] was obtained on the residue, yielding 1.9 g (97%)of 2-phenyl-1,3-oxathiolane. ¹H-NMR (CDCl₃): δ 1.74 (m, 1H), 2.11 (m,1H), 2.82, (m, 1H), 3.22 (m, 1H), 3.81 (m, 1H), 4.35 (m, 1H), 5.80 (s,1H), 7.36 (m, 3H), 7.49 (m, 2H). ¹³C-NMR (CDCl₃): δ 25.73, 29.26, 70.74,126.19, 128.46, 128.53, 139.52.

Example No. 15 Synthesis of 2-lithio-2-phenyl-1,3-oxathiane

To a solution of 2-phenyl-1,3-oxathiane from Example No. 14, (1.0 g, 5.5mmol) in THF (5.8 mL) and hexane (5 mL) was added n-BuLi (3.3 mL, 1.68 Min hexane) dropwise via a syringe at −78° C. The solution was stirredfor an additional 3 hours at −5° C. The resulting 0.39 M2-lithio-2-phenyl-1,3-oxathiane (abbreviated as POT-Li) was used as ananionic initiator for polymerizing butadiene and/or butadiene/styrene.

Example No. 16 Synthesis of Polybutadiene with2-lithio-2-phenyl-1,3-dithiane

Two 0.8 L bottles were charged with 163.6 g of hexane, and 136.4 g ofbutadiene blend (22 wt % in hexane). This was followed by 1.2 mL (Ex.16A) and 0.55 mL (Ex. 16B) of PDT-Li (from Ex. No. 13) added to theseparate bottles by syringe. The bottles were agitated and heated at 50°C. for 1.5 hours. The polymer cements were terminated with a smallamount of 2-propanol, treated with 4 mL of BHT solution; worked up with2-propanol, and dried under vacuum for 12 hours. It should be noted thatdue to the varying amounts of initiator used for Examples 16A and 16B,the resulting polymers had differing molecular weights, as seen in TableIII.

TABLE III Ex. No. 16 16A Initiator PDT-Li PDT-Li Amount (mL) 1.2 0.55M_(n) (kg/mol) 60.9 120.6 M_(w)/M_(n) 1.07 1.05

Example No. 17 Synthesis of Polybutadiene with2-lithio-2-phenyl-1,3-oxathiane

The preparation and the procedure used for Examples 16A and 16B wererepeated, using of POT-Li (as prepared in Ex. No. 15) as initiator. Themolecular weights of the polymers are listed hereinbelow. It should benoted that due to the varying amounts of initiator used for Examples 17Aand 17B, the resulting polymers had differing molecular weights, as seenin Table IV.

TABLE IV Ex. No. 17 17A Initiator POT-Li POT-Li Amount (mL) 0.96 0.70M_(n) (kg/mol) 99.4 126.9 M_(w)/M_(n) 1.08 1.16

Example No. 18 Synthesis of Poly(styrene-co-butadiene) with2-lithio-2-phenyl-1,3-dithiane

A 0.8 L bottle was charged with 190 g of hexane, 20 g of styrene blend,and 120 g of butadiene blend (22 wt % in hexane), then 0.61 mL of PDT-Li(Ex. No. 13) by syringe. The bottle was agitated and heated at 50° C.for 1.5 hours. The polymer cement was terminated with a small amount of2-propanol, treated with 4 mL of BHT solution, worked up with2-propanol, and drum dried. M_(n)=135.8 kg/mol, M_(w)/M_(n)=1.1,T_(g)=−69° C.

Example No. 19 Synthesis of Polybutadiene with In Situ2-lithio-2-phenyl-1,3-dithiane

A 0.8 L bottle was charged with 162.4 g of hexane, 137.6 g of butadieneblend (21.8 wt % in hexane), and 0.075 g of 2-phenyl-1,3-dithiane, then0.23 mL of n-BuLi (1.68 M in hexane) by syringe. The bottle was agitatedand heated at 50° C. for 1.5 hours. The polymer cement was terminatedwith a small amount of 2-propanol, treated with 4 mL of BHT solution;worked up with 2-propanol, and dried under vacuum for 12 hours. Presenceof the 2-phenyl-1,3-dithiane headgroup was confirmed by UV tracedetector, set at 254 nm used with the GPC. M_(n)=94.4 kg/mol,M_(w)/M_(n)=1.22, T_(g)=−72.7° C.

Comparative Example No. 20 Synthesis of Polybutadiene with n-BuLi

The preparation and the procedure used in Example 19 were repeated, butwithout adding 2-phenyl-1,3-dithiane. The product was a conventionalpolybutadiene. M_(n)=80.2 kg/mol, M_(w)/M_(n)=1.06, T_(g)=−94° C.

Example No. 21 Synthesis of 2-(4-dimethylamino)phenyl-1,3-dithiane

To an oven-dried 500 mL flask fitted with a magnetic stirring bar andreflux condenser was introduced 6.89 g (46.2 mmol) of4-(dimethylamino)benzaldehyde, 8.8 g (46.2 mmol) of p-toluenesulfonicacid monohydrate, and 180 mL of THF. The mixture was stirred for 10minutes, and then 2.5 g of Montmorillonite KSF was added, followed by 5g (46.2 mmol) of 1,3-propanedithiol in 30 mL of THF. The mixture wasrefluxed under nitrogen for 12 hours. After cooling to room temperatureand filtered, the filtrate was washed with saturated NaHCO₃ (2×100 mL),saturated NaCl (100 mL) and dried over MgSO₄ (anhydrous). The solventwas evaporated; a chromatograph using silica gel [elution withHexane/Et₂O (85/15)] was obtained on the residue, yielding 10.5 g (95%)of 2-[4-(dimenthylamino)]-phenyl-1,3-dithiane.

¹H-NMR (CDCl₃): δ 1.90 (m, 1H), 2.14 (m, 1H), 2.93, (s, 6H), 2.97 (m,4H), 5.11 (s, 1H), 6.67 (m, 2H), 7.33 (m, 2H), ¹³C-NMR (CDCl₃): δ 25.12,32.28, 40.46, 50.89, 112.28, 126.62, 128.46, 150.43.

Example No. 22 Synthesis of2-lithio-2-(4-dimethylamino)phenyl-1,3-dithiane

To a solution of 2-(4-dimethylamino)phenyl-1,3-dithiane (as prepared inExample No. 21, 1.25 g, 5.22 mmol in THF (8 mL) and Et₃N (1 mL)) wasadded n-BuLi (3.1 mL, 1.68 M in hexane) dropwise via a syringe at −78°C. The solution was stirred for an additional 4 hours at 0° C. Theresulting 0.43 M 2-lithio-2-(4-dimethyl-amino)phenyl-1,3-dithiane(abbreviated as DAPDT-Li) was used as anionic initiator for polymerizingbutadiene and/or butadiene/styrene and stored in an inert atmosphere ofnitrogen in a refrigerator.

Example No. 23 Synthesis of Polybutadiene with2-lithio-2-(4-dimethylamino)phenyl-1,3-dithiane

A 0.8 L bottle was charged with 180 g of hexane, and 152 g of butadieneblend (21.7 wt % in hexane), then 1.6 mL of DAPDT-Li (prepared inExample 22) was added by syringe. The bottle was agitated and heated at50° C. for 1.5 hours. The polymer cement was terminated with a smallamount of 2-propanol, treated with 5 mL of BHT solution; worked up with2-propanol, and dried under vacuum for 12 hours.

Example No. 24 Synthesis of Polybutadiene with2-lithio-2-(4-dimethylamino)phenyl-1,3-dithiane

The preparation and the procedure used in Example No. 23 were repeated,but using 1.0 mL of DAPDT-Li (prepared Example 22). All polymers wereanalyzed by GPC using styrene as the standard and in THF solution. Themolecular weights of the polymers are listed below.

TABLE V Example No. 23 24 Initiator DAPDT-Li DAPDT-Li M_(n) (kg/mol)53.0 96.3 M_(w)/M_(n) 1.028 1.033

All polymers were confirmed by UV trace detector, set at 254 nm usedwith the GPC.

Example No. 25 Synthesis of Poly(styrene-co-butadiene) with2-lithio-2-(4-dimethyl-amino)phenyl-1,3-dithiane

A 0.8 L bottle was charged with 188 g of hexane, 20.18 g of styreneblend (32.7%), and 122 g of butadiene blend (22 wt % in hexane), then0.7 mL of DAPDT-Li (prepared in Example 22) and 0.05 mL of cyclicoligomeric oxolanyl alkane modifier (1.6 M in hexane) were added bysyringe. The bottle was agitated and heated at 50° C. for 1.5 hours. Thepolymer cement was terminated with a small amount of 2-propanol, treatedwith 5 mL of BHT solution, work up with 2-propanol, and drum dried.M_(n)=107.4 kg/mol, M_(w)/M_(n)=1.11, T_(g)=−37.39° C.

Example No. 26 Synthesis of Poly(styrene-co-butadiene) with butyllithium

The procedure of Example No. 25 was repeated using an equivalent molaramount of n-butyllithium as the initiator. M_(n)=101.6 kg/mol,M_(w)/M_(n)=1.05, T_(g)=−41.2° C.

Example No. 27 Synthesis of Poly(styrene-cobutadiene) with2-lithio-2-(4-dimethyl-amino)phenyl-1,3-dithiane

A 0.8 L bottle was charged with 188 g of hexane, 20.18 g of styreneblend (32.7%), and 122 g of butadiene blend (22 wt % in hexane), then1.0 mL of DAPDT-Li (prepared in Example 22) was added by syringe, butwithout addition of a modifier. The bottle was agitated and heated at50° C. for 1.5 hours. The polymer cement was terminated with a smallamount of 2-propanol, treated with 5 mL of BHT solution, work up with2-propanol, and drum dried. M_(n)=115.2 kg/mol, M_(w)/M_(n)=1.1 kg/mol,T_(g)=−51.08° C.

Example No. 28 Synthesis of Poly(styrene-co-butadiene) with2-lithio-2-(4-dimethyl-amino)phenyl-1,3-dithiane

Into a two gallon (7.6 L) N₂ purged reactor, equipped with a stirrer,was added 1.619 kg of hexane, 0.414 kg of 33 wt % styrene in hexane, and2.451 kg of 22.2 wt % butadiene in hexane. The reactor was charged with21 mL of 0.3 M of 2-lithio-2-(4-dimethylamino)phenyl-1,3-dithiane(abbreviated as DAPDT-Li) and 1.05 mL of cyclic oligomeric oxolanylalkane modifier (1.6 M in hexane) and then heated to 24° C. The reactorjacket was then heated to 50° C. After 16 minutes, the batch temperaturepeaked at 66.7° C. After an additional 25 minutes, samples of the cementwere removed from the reactor into dried 28-oz (0.8 L) glass bottles,and terminated with one of the following: tributyltin chloride (3.68 M,abbreviated as DAPDT-SBR-SnBu3), 1,3-dimethyl-2-imidazolidinone (DMI,9.14 M, abbreviated as DAPDT-SBR-DMI), and isopropanol (abbreviated asDAPDT-SBR-H) at 50° C. bath for 30 minutes, respectively, coagulated inisopropanol containing butylated hydroxy toluene (BHT), and drum driedto yield polymers with following properties, as seen in Table VI:

TABLE VI Example No. 28A 28B 28C Description DAPDT- DAPDT-SBR-DMIDAPDT-SBR-SnBu3 SBR-H M_(n) (kg/mol) 110.0 66.0* 110.0 M_(w) (kg/mol)122.0 84.9* 120.0 T_(g) (° C.) −36.8 −37.0 −36.8 apparent M_(n) andM_(w) are low due to interaction of polymer with GPC columns.

Example No. 29 Synthesis of Poly(styrene-co-butadiene) with In-Situ2-lithio-2-(4-dimethyl-amino)phenyl-1,3-dithiane

The foregoing polymer was also prepared in situ as follows. To a twogallon (7.6 L) N₂ purged reactor equipped with a stirrer was added 1.610kg of hexane, 0.412 kg of 33 weight percent styrene in hexane, and 2.462kg of 22.1 weight percent butadiene in hexane. The reactor was thencharged a mixture of 1.36 g of 2-(4-dimethylamino)phenyl-1,3-dithiane in10 mL of THF and 1 mL of triethylamine with 3.37 mL of n-BuLi (1.68 M)in hexane, and agitated at 24° C. for 5 to 10 minutes, then 1.5 mL ofcyclic oligomeric oxolanyl modifies (1.6 M in hexane) was charged, andthe reactor jacket was then heated to 50° C. After 16 minutes, the batchtemperature peaked at 62.9° C. After an additional 15 minutes, thecement was removed from the reactor into dried 28 oz (0.8 L) glassbottles, terminated with 1,3-dimethyl-2-imidazolidinone (DMI, 9.14 M,abbreviated as DAPDT-SBR-DMI), and isopropanol (abbreviated asDAPDT-SBR-H) at 50° C. bath for 30 minutes, respectively, coagulated inisopropanol containing butylated hydroxy toluene (BHT), and drum driedto yield polymers with the following properties, as shown in Table VII:

TABLE VII Example No. 29A 29B Description DAPDT-SBR-H DAPDT-SBR-DMIM_(n) (kg/mol) 123.0 83.0* M_(w) (kg/mol) 135.0 94.0* T_(g) (° C.) −34.3−34.7 apparent M_(n) and M_(w) are low due to interaction of polymerwith GPC columns

The SBR polymer prepared according to Example No. 25 was utilized toprepare a vulcanizable elastomer, designated as Example No. 30. Forcomparison, a control polymer was prepared using n-butyllithium as theinitiator, from Example No. 26, and was designated as Example No. 31(Control). Both stocks contained carbon black as the reinforcing fillerand the formulations are provided in Table IV. Amounts listed arepresented by parts per hundred rubber (phr).

TABLE VIII Carbon Black Formulation Generic Compound CompoundFormulation Example 30 Example 31 MASTERBATCH Polymer 100 PolymerExample 25 100 Polymer Example 26 100 Carbon Black-N343 type 55 55 55Wax 1 1 1 Antiozonant 0.95 0.95 0.95 ZnO 2.5 2.5 2.5 Stearic Acid 2 2 2Processing Oil 10 10 10 Subtotal, Masterbatch 171.45 171.45 171.45 (phr)FINAL Masterbatch 171.45 171.45 171.45 Sulfur 1.3 1.3 1.3 Accelerators1.9 1.9 1.9 Total (phr) 174.65 174.65 174.65

The two compounds from Table VIII, Example Nos. 30 and 31, were nextcured and then subjected to physical testing, as set forth in Table IX,hereinbelow.

TABLE IX Compound Compound Example 30 Example 31 171° C. MDR t₅₀ (min):3.02 2.92 171° C. MH-ML (kg-cm): 16.9 20.9 ML₁₊₄ @ 130° C.: 21.8 27.1300% Modulus @ 23° C. 9.08 11.69 (Mpa): Tensile Strength @ 23° C. 15.7316.17 (Mpa): tan δ, 0° C., 0.5% E, 5 Hz: 0.1688 0.1790 tan δ, 50° C.,0.2% E, 5 Hz: 0.2831 0.2355 RDA 0.25-14% ΔG′ 4.8917 4.2280 (MPa): tan δ,50° C., 5.0% E, 1 Hz: 0.2620 0.2108 Bound Rubber (%): 10.1 19.0

The SBR polymer prepared according to Example No. 25 was then utilizedto prepare a vulcanizable elastomer with a combination of carbon blackand silica as fillers, and designated as Example No. 32. For comparison,control polymer Example No. 26, prepared using n-butyl lithium as theinitiator, was also used in the same carbon black/silica containingcompound (as Example No. 33). The complete formulations are provided inTable X. Amounts listed are presented by parts per hundred rubber (phr).

TABLE X Silica/Carbon Black Formulation Generic Compound CompoundFormulation Example 32 Example 33 MASTERBATCH Polymer 100 PolymerExample 100 25 Polymer Example 100 26 Silica 30 30 30 Carbon Black 35 3535 Antiozonant 0.95 0.95 0.95 Stearic Acid 1.5 1.5 1.5 LVA Oil 10 10 10Remill 60% Si75 on 4.57 4.57 4.57 carrier FINAL ZnO 2.5 2.5 2.5 Sulfur1.7 1.7 1.7 Accelerators 2.0 2.0 2.0 PVI 0.25 0.25 0.25 Total (phr)188.47 188.47 188.47

The resulting compounds, Example Nos. 32 and 33, were next cured andthen subjected to physical testing, as set forth in Table XI,hereinbelow.

TABLE XI Compound Compound Example 32 Example 33 171° C. MDR t₅₀ (min):6.49 8.37 171° C. MH-ML (kg-cm): 26.27 23.00 ML₁₊₄ @ 130° C.: 78.1 60.2300% Modulus @ 23° C. 9.8 7.1 (MPa): Tensile Strength @ 23° C. 14.3 10.3(MPa): tan δ, 0° C., 0.5% E, 5 Hz: 0.1572 0.1518 tan δ, 50° C., 0.2% E,5 Hz: 0.2190 0.2431 RDA 0.25-14% ΔG′ (MPa): 7.436 6.570 tan δ, 50° C.,5.0% E, 1 Hz: 0.2341 0.2707 Bound Rubber (%): 26.5 18.4

The data contained in Table XI demonstrates a 13.5% reduction in tan δfor the silica/carbon black reinforced compound containing the SBRpolymer with the initiator DAPDT-Li (Ex. No. 32) as compared to thecompound comprising the control polymer (Ex. No. 33).

Further examples were conducted and are reported as follows.

Example 34 Synthesis of Poly(styrene-co-butadiene) with2-lithio-2-(4-dimethyl-amino)phenyl-1,3-dithiane

Table XII below contains data characterizing the polymers resulting fromthree different methods of initiating the polymerization of anapproximately 110 kg/mol M_(n) butadiene and styrene copolymer in atwo-gallon (7.6 L) reactor. Initiation No. 1 involved the directaddition of 2-lithio-2-(4-dimethyl-amino)phenyl-1,3-dithiane; InitiationNo. 2 involved the addition of n-BuLi and2-(4-dimethyl-amino)phenyl-1,3-dithiane together; and Initiation No. 3involved the addition of 2-(4-dimethyl-amino)phenyl-1,3-dithiane andn-BuLi separately.

TABLE XII Initiation Number 1 2 3 M_(n) (kg/mol) 115.3 113.4 109.9M_(w)/M_(n) 1.09 1.08 1.35

Example 35 Synthesis of Poly(styrene-co-butadiene) with2-lithio-2-(4-dimethyl-amino)phenyl-1,3-dithiane In-Situ and Terminatedwith DMI

To a two gallon (7.6 L) N₂ purged reactor equipped with a stirrer wasadded 1.610 kg of hexane, 0.412 kg of 33 weight % styrene in hexane, and2.419 kg of 22.5 weight % butadiene in hexane. The reactor was thencharged a mixture of 1.36 g of 2-(4-dimethylamino)phenyl-1,3-dithiane in10 mL of THF and 1 mL of triethylamine with 3.37 mL of n-BuLi (1.68 M)in hexane, and agitated at 24° C. for 5 to 10 minutes, then 1.5 mL of1.6 M in hexane was charged, and the reactor jacket was then heated to50° C. After 16 minutes, the batch temperature peaked at 62.7° C. Afteran additional 15 minutes, the cement was removed from the reactor andplaced in dried 28-oz (0.8 L) glass bottles, then terminated with thefollowing: isopropanol (abbreviated as DAPDT-SBR-H) and1,3-dimethyl-2-imidazolidinone (DMI, 9.14 M, abbreviated asDAPDT-SBR-DMI), at 50° C. bath for 30 minutes, then coagulated inisopropanol containing butylated hydroxy toluene (BHT), and drum driedto yield the polymers with following properties:

TABLE XIII Example No. 35A 35B Description DAPDT-SBR-H DAPDT-SBR-DMIM_(n) (kg/mol) 108.5 68.7* M_(w) (kg/mol) 117.6 75.0* T_(g) (° C.) −29.7−29.9 ML₁₊₄ @ 100° C. 11.5 9.5 apparent M_(n) and M_(w) are low due tointeraction of polymer with GPC columns.

Example 36 Synthesis of Poly(styrene-co-butadiene) with n-BuLi

The preparation and the procedure used in Example 35 were repeated, andn-BuLi (1.68 M in hexane) was used as an anionic polymerizationinitiator. The polymers with the following properties are used as thecontrol.

TABLE XIV Example No. 36A 36B Description n-Bu-SBR-H n-Bu-SBR-DMI M_(n)(kg/mol) 110.6 97.1* M_(w) (kg/mol) 114.8 100.5* T_(g) (° C.) −29.9−29.9 ML₁₊₄ @ 100° C. 7.0 7.5 apparent M_(n) and M_(w) are low due tointeraction of polymer with GPC columns.

Application in Rubber Compounds

The SBR polymers prepared according to Examples 35-36 were utilized toprepare a vulcanizable elastomeric compound that contained carbon blackas the reinforcing filler. The compound formulation used was the genericformulation shown in Table VIII hereinabove. The results of physicaltesting are presented in Table XV.

TABLE XV Compound Example No.: 37 38 39 40 Polymer Example. No: 36A 36B35A 35B 171° C. MDR t₅₀ (min): 3.11 1.99 3.04 1.93 171° C. MH-ML(kg-cm): 17.3 16.5 20.9 19.3 ML₁₊₄ @ 130° C.: 24.3 37.8 29.2 42.4 300%Modulus @ 23° C. 10.92 14.39 12.87 15.61 (MPa): Tensile Strength @ 23°C. 15.37 15.75 15.42 16.93 (MPa): Tan δ, 0° C., 0.5% E, 5 Hz: 0.26660.3425 0.2795 0.3516 tan δ, 50° C., 0.2% E, 5 Hz: 0.2770 0.1744 0.25080.1522 RDA 0.25-14% ΔG′ 4.67 0.51 4.09 0.55 (MPa): tan δ, 50° C., 5.0%E, 1 Hz: 0.2710 0.1130 0.2244 0.0894

As can be seen in Table XV, compounding carbon black with the SBRpolymer prepared in-situ with the initiator DAPDT-Li (Compound ExampleNo. 39), provided a 17.2% reduction in tan δ at 50° C., compared to thecompound containing the control polymer prepared with n-BuLi initiator(Compound Example No. 37). Likewise, the DAPDT-SBR-DMI containingcompound (Compound Example No. 40) provided a 20.9% reduction in tan δat 50° C., compared to the compound containing the control n-Bu-SBR-DMIpolymer (Compound Example No. 38).

Application in Rubber Compounds

The SBR polymers (Examples 35A and 35B) prepared according to ExampleNo. 35 were utilized to prepare a vulcanizable elastomeric compound witha combination of carbon black and silica as fillers, designated asCompound Example Nos. 41 and 42. For comparison, compounds containingthe control polymers (Example Nos. 36A and 36B) were prepared using thecombination carbon black/silica formulation, and designated as CompoundExample Nos. 43 and 44. The carbon black/silica formulation used forCompound Example Nos. 41-44 was the generic formulation shown in Table Xhereinabove.

TABLE XVI Compound Example No.: 43 44 41 42 Polymer Example No.: 36A 36B35A 35B 171° C. MDR t₅₀ (min): 7.27 5.02 6.46 3.84 171° C. MH-ML(kg-cm): 22.15 17.81 24.81 21.67 ML₁₊₄ @ 130° C.: 53.9 91.1 69.9 100.7300% Modulus @ 23° C. 8.3 10.9 10.0 13.4 (MPa): Tensile Strength @ 23°C. 12.2 14.9 14.4 16.6 (MPa): tan δ, 0° C., 0.5% E, 5 Hz: 0.2602 0.29260.2665 0.3200 tan δ, 50° C., 0.2% E, 5 Hz: 0.2628 0.1980 0.2377 0.1744RDA 0.25-14% ΔG′ (MPa): 8.231 2.240 6.562 1.766 tan δ, 50° C., 5.0% E, 1Hz: 0.2578 0.1743 0.2244 0.1318

As can be seen in Table XVI, formulating a silica/carbon black compoundwith a SBR polymer prepared in-situ with the initiator DAPDT-Li provideda 13% reduction in tan δ at 50° C., compared to the control compoundcontaining the polymer prepared with n-BuLi initiator (Compound ExampleNos. 41 and 43). The DAPDT-SBR-DMI containing silica/carbon blackcompound also provided a 24.4% reduction in tan δ at 50° C., compared tothe n-Bu-SBR-DMI containing silica/carbon black compound (CompoundExample Nos. 42 and 44).

Further examples were conducted to study the properties of terminatedpolymers according to the present invention having head and tailfunctionality.

Example 45 Synthesis of 2-lithio-2-methyl-1,3-dithiane Initiated Polymer

To a 19 L reactor was added 4.75 kg hexane, 1.25 kg 33% styrene inhexane, and 7.55 kg 21.7 wt % butadiene in hexane. Then, 37.1 mL of 0.5M 2-methyl-1,3-dithiane in hexanes, 11.04 mL of 1.68 M butyl lithium inhexanes, and 3.83 mL of 1.6 M of a cyclic oligomeric oxolanyl alkanemodifier in hexane were added. The batch was then heated to 48.9° C.After 22 minutes, the reactor jacket was flooded with cold water. Afteran additional 41 minutes, 3.08 kg of polymer cement was discharged fromthe reactor into isopropanol containing butylated hydroxy toluene (BHT).The polymer was coagulated and drum dried and had the followingproperties: M_(n)=93.7 kg/mol, M_(w)=98.3 kg/mol, T_(g)=−31.3° C., %styrene=20.2, % block styrene=2.2%, % 1,2 butadiene=44.9%.

Example 46 Synthesis of 2-lithio-2-methyl-1,3-dithiane Initiated andtetraethylorthosilicate (TEOS) Terminated Polymer

An additional 2.36 kg of cement prepared in Example 45 was removed undernitrogen from the reactor. This was terminated with 1 eq. of TEOS perBuLi. The resulting polymer was coagulated in isopropanol and drum driedto yield a polymer with the following properties: M_(n)=219 kg/mol,M_(w)=385 kg/mol, T_(g) −31.5° C., % styrene=20.6, % block styrene=2.0%,% 1,2 butadiene=45.6%.

Example 47 Synthesis of 2-lithio-2-methyl-1,3-dithiane initiated and2-methylthio-2-thiazoline Terminated Polymer

An additional 2.21 kg of cement prepared in Example 45 was removed undernitrogen from the reactor. This was terminated with 1 eq. of2-methylthio-2-thiazoline per BuLi. The resulting polymer was coagulatedin isopropanol and drum dried to yield a polymer with the followingproperties: M_(n) 111 kg/mol, M_(w) 126 kg/mol, T_(g) −30.9° C., %styrene 20.7, % block styrene 1.9%, % 1,2 butadiene 45.5%.

Example 48 Synthesis of 2-lithio-2-methyl-1,3-dithiane Initiated andTributyltin Chloride Terminated Polymer

An additional 2.36 kg of cement prepared in Example 45 was removed undernitrogen from the reactor. This was terminated with 1 eq. of Bu₃SnCl perBuLi. The resulting polymer was coagulated in isopropanol and drum driedto yield a polymer with the following properties: M_(n) 106 kg/mol,M_(w) 113 kg/mol, T_(g) −31.3° C., % styrene 21.0, % block styrene 2.0%,% 1,2 butadiene 45.6%.

The foregoing polymers were compounded with carbon black following thegeneric formulation set forth in Table VIII (Compound Example Nos.49-52) and with a mixture of silica/carbon black following the genericformulation set forth in Table X hereinabove (Compound Example Nos.53-57). Next, the resulting compounds were cured and subjected tophysical testing, as set forth in Tables XVII and XVIII below.

TABLE XVII Carbon Black Formulation Compound Example No. 49 50 51 52Polymer Example No. 45 46 47 48 ML₁₊₄ @ 130° C. 18.7 61.9 34.2 27.8 300%Modulus @ 23° C. 9.69 12.34 12.53 11.48 (MPa): Tensile Strength @ 23° C.13.51 15.65 15.08 14.84 (MPa): tan δ, 0° C., 0.5% E, 5 Hz: 0.398 0.4330.445 0.433 tan δ, 50° C., 0.2% E, 5 Hz: 0.285 0.229 0.209 0.229 RDA0.25-14% ΔG′ (MPa): 5.237 2.994 1.187 1.598 tan δ, 50° C., 5.0% E, 1 Hz:0.282 0.210 0.149 0.176 Bound Rubber (%): 10.9 42.6 34.4 31.5

TABLE XVIII Silica/Carbon Black Formulation Compound Example No. 53 5455 56 Polymer Example No. 45 46 47 48 ML₁₊₄ @ 130° C. 46.7 96.5 73.062.7 300% Modulus @ 23° C. 8.22 12.70 10.68 10.24 (MPa): TensileStrength @23° C. 10.31 15.49 13.27 12.11 (MPa): tan δ, 0° C., 0.5% E, 5Hz: 0.348 0.415 0.386 0.382 tan δ, 50° C., 0.2% E, 5 Hz: 0.248 0.2020.222 0.224 RDA 0.25-14% ΔG′ (MPa): 8.028 3.732 4.358 5.170 tan δ, 50°C., 5.0% E, 1 Hz: 0.252 0.176 0.199 0.209

As can be seen in Tables XVII and XVIII, formulating carbon black andsilica/carbon black reinforced SBR polymers prepared with the initiator2-lithio-2-methyl-1,3-dithiane and then providing terminal functionality(Compound Example Nos. 50-52, 54-56) provided a reduction in tan δcompared to the polymer prepared with the initiator but not functionallyterminated (Compounds Example Nos. 49 and 53).

Based upon the foregoing disclosure, it should now be apparent that theuse of the anionic polymerization initiators described herein provides auseful method for the polymerization of diene and monovinyl aromaticmonomers. As should be evident from the data provided in the tablesherein, presence of the functional groups, according to the presentinvention, on polymers from which vulcanizable elastomeric compositionscan be made can provide improved physical properties in various articlessuch as tires and the like, compared with the same polymers which do notcarry these functional groups.

It is, therefore, to be understood that any variations evident fallwithin the scope of the claimed invention and thus, the selection ofspecific component elements can be determined without departing from thespirit of the invention herein disclosed and described. In particular,anionic polymerization initiators according to the present invention arenot necessarily limited to those dithianes exemplified herein.

Various modifications and alterations that do not depart from the scopeand spirit of this invention will become apparent to those skilled inthe art. This invention is not to be duly limited to the illustrativeembodiments set forth hereinabove. Thus, the scope of the inventionshall include all modifications and variations that may fall within thescope of the attached claims.

1. A vulcanized rubber composition comprising: the vulcanization productof a functional polymer, where the functional polymer is defined by theformula

where R is selected from C₁ to C₆ trialkyl-silyl groups, C₁ to C₂₀ alkylgroups, C₄ to C₂₀ cycloalkyl groups, C₆ to C₂₀ aryl groups, thienyl,furyl, and pyridyl groups; and R may optionally have attached theretoany of the following functional groups: C₁ to C₁₀ alkyl groups, C₆ toC₂₀ aryl groups, C₂ to C₁₀ alkenyl groups, C₃ to C₁₀ non-terminalalkynyl groups, ethers, tert-amines, oxazolines, thiazolines,phosphines, sulfides, silyls, and mixtures thereof; where R¹ is selectedfrom C₂ to C₈ alkylene groups, where X is NR, and where π is a polymerchain.
 2. The vulcanized rubber of claim 1, where said polymer chainderives from the anionic polymerization of monomer including conjugateddienes and optionally vinyl aromatics.
 3. The vulcanized rubber of claim1, where said polymer chain includes a terminal functional group thatincludes a trialkyltin group, a thiazoline group, a trialkoxysilanegroup, or a carboxamide group.
 4. The vulcanized rubber of claim 1,where said polymer chain includes a terminal group resulting from thetermination of said polymer chain with a reagent selected from the groupconsisting of tin tetrachloride, tributyltin chloride, dibutyltinchloride, tetraethylorthosilicate, 1,3-dimethyl-2-imidazolidinone, andmixtures thereof.
 5. The vulcanized rubber of claim 1, where the rubbercomposition further comprises a filler selected from the groupconsisting of carbon black, silica, starch, aluminum hydroxide,magnesium hydroxide, clays, and mixtures thereof.
 6. The vulcanizedrubber of claim 2, where R includes a C₆ to C₂₀ aryl group havingattached thereto a tert-amine group.
 7. A tire component comprising therubber composition of claim
 1. 8. A tire comprising: a tread prepared byvulcanizing a rubber composition including (i) a first elastomerselected from the group consisting of natural rubber, polyisoprene,polybutadiene, poly(styrene-co-butadiene), poly(styrene-co-isoprene),poly(styrene-co-isoprene-co-butadiene), poly(isoprene-co-butadiene), andmixtures thereof; (ii) a second elastomer that is a functional polymerdefined by the formula

where R is selected from C₁ to C₆ trialkyl-silyl groups, C₁ to C₂₀ alkylgroups, C₄ to C₂₀ cycloalkyl groups, C₆ to C₂₀ aryl groups, thienyl,furyl, and pyridyl groups; and R may optionally have attached theretoany of the following functional groups: C₁ to C₁₀ alkyl groups, C₆ toC₂₀ aryl groups, C₂ to C₁₀ alkenyl groups, C₃ to C₁₀ non-terminalalkynyl groups, ethers, tert-amines, oxazolines, thiazolines,phosphines, sulfides, silyls, and mixtures thereof; where R¹ is selectedfrom C₂ to C₈ alkylene groups, where X is NR, and where π is a polymerchain; (iii) carbon black, (iv) silica; and (v) a curative.
 9. The tireof claim 8, where the ratio of carbon black to silica is from about 10:1to about 1:4.
 10. The tire of claim 8, where the rubber compositionfurther includes a coupling agent, a processing oil, an antidegradant, astearic acid, zinc oxide, sulfur, and an accelerator.
 11. The tire ofclaim 8, where said polymer chain derives from the anionicpolymerization of monomer including conjugated dienes and optionallyvinyl aromatics.
 12. The tire of claim 8, where said polymer chainincludes poly(styrene-co-butadiene).
 13. The tire of claim 8, where saidpolymer chain includes a terminal functional group that includes atrialkyltin group, carbodiiamides, a thiazoline group, a trialkoxysilanegroup, or a carboxamide group.
 14. The tire of claim 8, where saidpolymer chain includes a terminal group resulting from the terminationof said polymer chain with a reagent selected from the group consistingof tin tetrachloride, tributyltin chloride, dibutyltin dichloride,tetraethylorthosilicate, 1,3-dimethyl-2-imidazolidinone, alkylthiothiazolines, and mixtures thereof.
 15. The tire of claim 8, where Rincludes a C₆ to C₂₀ aryl group having attached thereto a tert-aminegroup.
 16. The tire of claim 8, where π is an elastomer.
 17. The tire ofclaim 16, where π has a number average molecular weight of from about0.5 to about 500 kg/mole.
 18. The tire of claim 12, where the ratio ofunits deriving from diene to units deriving from styrene is from about95:5 to about 65:35.
 19. The tire of claim 17, where the terminalfunctional group derives from terminating a living polymer with acompound defined by one of the formulae Si(OR)₄, RSi(OR)₃, or R₂Si(OR)₂,where R is an organic moiety.